529. The examples in [§ 528] show that most cases of ellipsis fall under two heads:

1. To avoid repetition, words are often omitted in one part of the sentence when they occur in another part.

2. Pronouns, the conjunction that, and some forms of the verb is, are often omitted when they are readily supplied.

Under the second head come (1) the ellipsis of the subject (thou or you) in imperative sentences ([§ 268]), (2) that of relative pronouns in the objective case ([§ 151]), (3) that of is, are, etc. (with the subject pronoun) in subordinate clauses introduced by when, though, if, and the like ([§§ 397], [399], [417]).

Note. The so-called “telegraphic style” omits I with any verb or with all verbs. It should be confined to telegrams, where space is money.

530. Adverbs indicating direction (like forward, back) are often used without a verb in imperative sentences.

Note. In older English, the omission of the verb of motion was common, even in sentences not imperative, as in the following examples from Julius Cæsar:—“We’ll along ourselves, and meet them”; “Shall we on, and not depend on you?”

531. The ellipsis of the subordinate conjunction that is very common, especially in indirect discourse ([§§ 388], [433]).